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Oxygen Binding by the Hemocyanin of the Terrestrial Hermit Crab Coenobita Clypeatus (Herbst): The Effect of Physiological Parameters in vitro

1986; University of Chicago Press; Volume: 59; Issue: 6 Linguagem: Inglês

10.1086/physzool.59.6.30158608

1937-4267

Stephen Morris, C. R. Bridges,

Neurobiology and Insect Physiology Research

In situ, the terrestrial hermit crab Coenobita clypeatus may be exposed to extremes of temperature together with the associated problems of dehydration. In the present in vitro study, the effect of temperature on hemocyanin oxygen affinity was small over the range 25-30 C (ΔH = -14.8 kJ · mol⁻¹). Outside this range, however, changes in enthalpy were >39 kJ · mol⁻¹. Changes in calcium and hemocyanin concentration over the range expected in vivo did not appreciably affect oxygen affinity. A dilution of the hemocyanin concentration to 50% of the original value decreased oxygen affinity only slightly. The addition of L-lactate, a known effector of hemocyanin oxygen affinity to nondialyzed and dialyzed hemolymph, did not influence hemocyanin oxygen affinity. The hemolymph of Coenobita contained a large amount of urate (~1 mM) and 1.2 mM L-lactate. The removal of this ion, also an effector of hemocyanin oxygen affinity, resulted in a hemolymph preparation that exhibited the same oxygen-binding properties as whole hemolymph. The hemocyanin-free plasma of Coenobita was, however, capable of increasing the O₂ affinity of crayfish hemocyanin, confirming that Coenobita hemocyanin itself is extremely insensitive to identified effectors of hemocyanin oxygen affinity in other crustaceans.